Stereoselective Synthesis of (E)-Hydroxystilbenoids by Ruthenium-Catalyzed Cross-Metathesis

Fast Initiating Furan-Containing Hoveyda-Type Complexes: Synthesis and Applications in Metathesis Reactions

Two new ruthenium complexes with chelating-ether benzylidene ligands bearing a furan moiety were synthesized and characterized, including X-ray crystallography. They initiated fast, also at 0 °C, and were found to be highly active in a variety of ring-closing, ene-yne, and cross-metathesis reactions, including an active pharmaceutical ingredient (API) model, which makes them good candidates for the transformation of complex polyfunctional compounds that require mild reaction conditions.

An Update on Pharmacological Relevance and Chemical Synthesis of Natural Products and Derivatives with Anti SARS-CoV-2 Activity

Natural products recognized traditionally as a vital source of active constituents in pharmacotherapy. The COVID-19 infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly transmissible, pathogenic, and considered an ongoing global health emergency. The emergence of COVID-19 globally and the lack of adequate treatment brought attention towards herbal medicines, and scientists across the globe instigated the search for novel drugs from medicinal plants and natural products to tackle this deadly virus. The natural products rich in scaffold diversity and structural complexity are an excellent source for antiviral drug discovery. Recently the investigation of several natural products and their synthetic derivatives resulted in the identification of promising anti SARS-CoV-2 agents. This review article will highlight the pharmacological relevance and chemical synthesis of the recently discovered natural product and their synthetic analogs as SARS-CoV-2 inhibitors. The summarized information will pave the path for the natural product-based drug discovery of safe and potent antiviral agents, particularly against SARS-CoV-2.

Supramolecular gels derived from nucleoside based bolaamphiphiles as a light-sensitive soft material

Light-sensitive Low Molecular Weight Gelators (LMWGs) derived from glyconucleoside bolaamphiphiles containing a stilbene unit displayed gelation abilities in hydroalcoholic mixtures. These materials showed a gel-sol transition under UV irradiation thanks to E-Z isomerization of stilbene and could find potential applications as drug delivery systems.

Synthesis of Stilbene and Chalcone Inhibitors of Influenza A Virus by SBA-15 Supported Hoveyda-Grubbs Metathesis

Stilbene and chalcone derivatives with biological activity against influenza A virus have been synthesized by self-, cross-, and ring-closing metathesis procedures. The reactions were performed under environmentally friendly conditions using the second generation Hoveyda-Grubbs catalyst Aquamet SiPr after immobilization on Santa Barbara Amorphous mesoporous silicate SBA-15. Irrespective from the experimental conditions, the heterogeneous catalyst showed activity and selectivity comparable than the homogeneous counterpart for at least six successive runs without appreciable leaching of the active species. An appreciable antiviral activity against influenza A virus for some of the novel derivatives were observed, mainly involving the early stage of the virus-replication life-cycle.

Exploring Anti-Prion Glyco-Based and Aromatic Scaffolds: A Chemical Strategy for the Quality of Life

Prion diseases are fatal neurodegenerative disorders caused by protein misfolding and aggregation, affecting the brain progressively and consequently the quality of life. Alzheimer’s is also a protein misfolding disease, causing dementia in over 40 million people worldwide. There are no therapeutics able to cure these diseases. Cellular prion protein is a high-affinity binding partner of amyloid β (Aβ) oligomers, the most toxic species in Alzheimer’s pathology. These findings motivate the development of new chemicals for a better understanding of the events involved. Disease control is far from being reached by the presently known therapeutics. In this review we describe the synthesis and mode of action of molecular entities with intervention in prion diseases’ biological processes and, if known, their role in Alzheimer’s. A diversity of structures is covered, based on glycans, steroids and terpenes, heterocycles, polyphenols, most of them embodying aromatics and a structural complexity. These molecules may be regarded as chemical tools to foster the understanding of the complex mechanisms involved, and to encourage the scientific community towards further developments for the cure of these devastating diseases.

A facile and rapid access to resveratrol derivatives and their radioprotective activity

A facile and rapid access to resveratrol derivatives has been achieved based on palladium-catalyzed oxidative Heck reaction of aryl boronic acids with styrenes followed by demethylation in moderate to good yields. A series of resveratrol derivatives with various functional groups has been synthesized easily. The radioprotective activity of synthesized compounds has also been evaluated using rat thymocytes. The results revealed that some resveratrol derivatives efficiently protected the thymocytes from radiation-induced apoptosis.

Ethenolysis: A Green Catalytic Tool to Cleave Carbon-Carbon Double Bonds

Remarkable innovations have been made in the field of olefin metathesis due to the design and preparation of new catalysts. Ethenolysis, which is cross-metathesis with ethylene, represents one catalytic transformation that has been used with the purpose of cleaving internal carbon-carbon double bonds. The objectives were either the ring opening of cyclic olefins to produce dienes or the shortening of unsaturated hydrocarbon chains to degrade polymers or generate valuable shorter terminal olefins in a controlled manner. This Review summarizes several aspects of this reaction: the catalysts, their degradation in the presence of ethylene, some parameters driving their productivity, the side reactions, and the applications of ethenolysis in organic synthesis and in potential industrial applications.

Tandem catalysis versus one-pot catalysis: ensuring process orthogonality in the transformation of essential-oil phenylpropenoids into high-value products via olefin isomerization–metathesis

One-pot and tandem catalysis methodologies are explored in developing efficient isomerization–metathesis routes to high-value cinnamates and ferulates from essential-oil allylbenzenes.

Improved synthesis of bioactive stilbene derivatives applying design of experiments to the Heck–Matsuda reaction

Design of experiments (DOE) was instrumental to optimize reaction conditions which allowed the efficient synthesis of key bioactive stilbenes.

Scope and limitations of the Heck-Matsuda-coupling of phenol diazonium salts and styrenes: a protecting-group economic synthesis of phenolic stilbenes

4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4'-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior.

Picea mariana bark: a new source of trans-resveratrol and other bioactive polyphenols

The ethyl acetate soluble fraction obtained from the hot water extract of Picea mariana bark (BS-EAc(f)) has been demonstrated to have anti-inflammatory and antioxidant properties. Thus, in the current study, we isolated and characterised major compounds of this fraction by HPLC, NMR and MS analyses. On the whole, 28 compounds were identified, among which were five neolignans, seven lignans, trans-resveratrol, three phenolic acids and four flavonoids. To the best of our knowledge, 2,3-dihydro-3-(4-hydroxy-3-methoxyphenyl)-2-(hydroxymethyl)-(2S,3S)-1,4-benzodioxin-6-propanol, threo and erythro 3-methoxy-8,4'-oxyneolignan-3',4,7,9,9'-pentol, pallasiin, (±) epi-taxifolin, homovanillyl alcohol, orcinol and 2-[4-(3-hydroxypropyl)-2-methoxyphenoxy]-1,3-propanediol are reported for the first time in the Picea genus. P. mariana dry bark contains at least 104μgg(-1)dw of trans-resveratrol and it could be therefore considered as a new accessible source of this molecule. This study provides novel information about the identity of major compounds present in BS-EAc(f), which is essential for the understanding of the anti-inflammatory and nutraceutical potential of this extract.

Stereoselectivity of supported alkene metathesis catalysts: a goal and a tool to characterize active sites

Stereoselectivity in alkene metathesis is a challenge and can be used as a tool to study active sites under working conditions. This review describes the stereochemical relevance and problems in alkene metathesis (kinetic vs. thermodynamic issues), the use of (E/Z) ratio at low conversions as a tool to characterize active sites of heterogeneous catalysts and finally to propose strategies to improve catalysts based on the current state of the art.

Consecutive palladium-catalyzed Hiyama-Heck reactions in aqueous media under ligand-free conditions

Symmetric and asymmetric (E)-1,2-diarylethenes are synthesized from aryl bromides by consecutive one-pot Hiyama-Heck reactions carried out in water and under air; the only additives required are sodium hydroxide, palladium acetate and poly(ethylene glycol), and the products are isolable in many cases by simple filtration of the water solution.

Synthesis and cytotoxic evaluation of a series of resveratrol derivatives

A total of 17 resveratrol (=(E)-5-[2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol) derivatives were synthesized from resveratrol (RES) through a facile approach. Among them, 13 compounds, 2 and 6-17, were reported for the first time, while 1 and 3-5 had already been reported several years ago. The cytotoxic activities of these compounds were evaluated against human nasopharyngeal epidermoid tumor cell line KB, and compounds 1 and 8-11 showed strong anticancer activities in vitro, comparable with that of 5-fluorouracil, an anticancer drug. On the basis of the experimental data obtained, structure-activity relationships are discussed.

Stereoselective synthesis of olefins by a reductive coupling reaction

Ketones and aldehydes are converted to symmetrical and (E)-olefins (1-15) by reaction with 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (PhPSe(2))(2), Woollins' reagent, in refluxing toluene; use of diketones was demonstrated by the reaction of PhC(O)CH(2)C(O)Ph which gives 1,2,4,5-tetraphenylbenzene (16) in 83% yield.